As known in the art, telephone services may be supported by circuit-switched telephone networks, either fixed or mobile, and by packet-switched networks.
More particularly, mobile telephone networks, such as for instance GSM (“Global System for Mobile communications”) and UMTS (“Universal Mobile Telecommunication System”), allow users to access telephone services through mobile terminals. A mobile telephone network is typically split in geographical areas which are termed “cells”. Mobile terminals moving across a mobile telephone network may pass from cell to cell without undergoing service interruption.
On the other hand, packet-switched telephone networks are capable of supporting telephone services thanks to special protocols such as Voice over IP (briefly, VoIP), which is adapted to support real time transport of voice traffic through packets in an IP network. For accessing telephone services offered by a packet-switched network, a user is typically connected to the packet-switched network by means of an access network. An access network typically comprises a wired tree-like network (for instance ADSL, Optical Access Networks (OAN), or the like), each user-side termination of the tree being provided with an access device. Each access device may be connected to user terminals either through a wired connection or a wireless connection.
In case of wireless connection, the access device substantially comprises a bi-directional radio transceiver. For instance, in the wireless technology called Wi-Fi (Wireless Fidelity), such access devices are called “hotspots”. User terminals are connected to an access device (and then to the packet-switched network) when they are located within the coverage area of the access device and when they are registered on the access device. Communication between the wireless access device and terminals is performed by using unlicensed frequencies. Access devices may be located in home environment, in office environment, or in public environment (railway stations, airport lounges, restaurants, or the like).
In the following description and in the claims, the expression “access device” will indicate a wireless access device for communicating with a given terminal through unlicensed frequencies, such as those used in the above mentioned Wi-Fi, Bluetooth or the like. The above cited “hotspots” are examples of said access devices. The expression “access network” will indicate a portion of a packet-switched network comprising one or more access devices.
In the art, dual mode terminals are known. A dual mode terminal is capable of being used either as a mobile terminal of a mobile telephone network, or as a wireless terminal of an access network connected to a packet-switched network external to the mobile telephone network. In the following description, the expression “cellular mode” will indicate a first mode of a dual mode terminal, wherein the dual mode terminal is employed as a mobile terminal of a mobile telephone network. On the other hand, the expression “wireless mode” will indicate a second mode of a dual mode terminal, wherein the dual mode terminal is employed as a wireless terminal of an access network connected to a packet-switched network.
In case a dual mode terminal is located within a coverage area of an access device, and the coverage area is within a cell of a mobile telephone network, the dual mode terminal is capable of working either in its wireless mode or in its cellular mode. Mode can be selected manually by the user, or it can be automatically selected by the dual mode terminal itself, according to various criteria (connection cost, or the like). When the dual mode terminal exits the coverage area of the access device, it can work only in cellular mode.
Operators of mobile circuit-switched telephone networks have developed technologies such as the Unlicensed Mobile Access (briefly, UMA), which allow an operator of a mobile telephone network to deal packet-switched networks and access networks as “extensions” of their mobile telephone network. In this way, a user provided with a dual mode terminal can access telephone services offered by the mobile telephone network even in wireless mode.
Among the various telephone services, a known telephone service allows a user to forward calls addressed to a given terminal also to terminals other than the originally called terminal.
U.S. Pat. No. 5,963,864 describes a method for providing telecommunication extension service to a subscriber with at least a first unit having a first number and a second unit having a second number. Upon receipt of a communication directed to the number associated with the one of the units, ringing is provided to both units. A party may answer either unit, or both units may be answered. If one unit is answered, then the other unit is provided with ringing for a predetermined number of rings or for a pre-selected amount of time.
US patent application 2002/0077098 A1 describes a method for dual ringing of a Centrex line and a wireless extension of the Centrex line. With dual ringing functionality, a single destination number dialed by a calling party results in ringing of both a Centrex line and a wireless extension of the Centrex line. In one preferred embodiment described therein, the dual ringing functionality is implemented with a network element (e.g., a service node) separate from a switch (e.g., a service signal point).
US patent application 2006/0019667 describes a method for providing integrated wireless and wired data voice and data services via a dual mode telecommunications device. A communication directed to an address associated with a dual mode device is received. If the dual mode device is in range of a wireless access point connected to a wired data network, then a determination is made whether the address of the dual mode device is associated with an address of at least one other device associated with the wired data network. If the address of the dual mode device is associated with an address of at least one other device associated with the wired data network, then the communication is routed over the wired data network to the dual mode device and the at least one other device.